The latest advances in wireless networks have enabled applications such as home and industrial automation; environment monitoring and sensing, security and surveillance; human and goods tracking; and medical monitoring.
In a wireless network, each node can communicate with other nodes that are within transmission range. Each node has a unique identity to facilitate communication among the nodes. Address assignment in an ad hoc network is a problem due to the irregular and spontaneous nature of the network topology.
Some addressing schemes, such as the one used by the ZigBee Alliance, use a hierarchical tree of addresses. For example, a ZigBee coordinator (ZC) node initially has control over all allocated addresses. Subsequently, a parent node, beginning with the ZC node, allocates a portion of its address space to a child node when the child node joins network. Because the number of child nodes for any parent node is fixed as a configuration parameter, it is possible to systematically determine the portions of the address space that is allocated to a joining child node. That facilitates route discovery without explicit route discovery via broadcast messages.
However, the static structure of the ZigBee scheme can waste addresses, or even deny some parent nodes from assigning addresses to potential child nodes. In addition, there is a restriction on the maximum number of levels that the addressing tree can have in the network. Furthermore, a failure of a single node can make nodes with addresses lower in the tree inaccessible. This is a serious problem when the failed node is near the root of the tree.
Another addressing scheme uses a distributed dynamic address assignment protocol, S. Nesargi and R. Prakash, “MANETconf: Configuration of Hosts in a Mobile Ad Hoc Network,” Proceedings of IEEE Infocom, June 2002. The protocol is based on a mutual exclusion process based on the Ricart-Agrawala algorithm, G. Ricart and A. K. Agrawala, “An optimal algorithm for mutual exclusion in computer networks,” Comm. ACM, 24(1), pp. 9-17, 1981. A joining node selects a neighboring node as an initiator node. The initiator node selects an address and broadcasts a message to notify all other nodes in the network of the selected address. Then, the initiator node waits for responses from the other nodes in the network. If the responses from all of the nodes are positive, meaning no other node is using the selected address, then the initiator node assign this address to the joining node. Otherwise, the initiator node selects another address, and so forth.
However, there are several problems with that protocol. All nodes must maintain information about the allocated addresses. This requires memory, which is a limited resource in small sensor nodes. In addition, the broadcast messages and other management messages consume network resources such as bandwidth and power. Moreover, the initiator node can select any address. Therefore, the address assignment does not necessarily follow a regular or systematic pattern. This makes route discovery a problem.
Another addressing scheme uses a binary split algorithm, M. Mohsin and R. Prakash, “IP Address Assignment in a Mobile Ad Hoc Network,” IEEE Military Communications Conference (MILCOM 2002), volume 2, pp. 856-861, October 2002. Each node maintains a block of available addresses. When a node wants to join the network, the joining node requests an address from a neighboring configuring node. The configuring node splits the block into two halves, and retains one half for itself and gives the other half to the requesting node. Every node maintains an address table to record the blocks of addresses. Each node also broadcasts periodically its block of addresses to enable other nodes to update their address tables. Addresses can also be ‘borrowed’ from other nodes. That scheme also leads to an address assignment that does not follow a regular or systematic pattern.
Another scheme performs duplicate address detection, C. E. Perkins, J. T. Malinen, R. Wakikawa, E. M. Belding-Royer, and Y. Sun, “IP Address Autoconfiguration for Ad Hoc Networks,” IETF Internet Draft, draft-ietf-manet-autoconf-01.txt, November 2001. A joining node selects two random addresses for itself, each from a different group of available addresses. One address is used as a temporary source address for a verification process. The other address is intended for a final address assignment, pending the verification process. That scheme also requires a large number of broadcast messages, and addresses are generated randomly.